1. Field
The subject invention is in the field of holders for products used in people's hands, such as holders for knives, utensils, tools and paper products. More specifically it is in the field of holders for paper products and, still more particularly, paper towels.
2. Prior Art
There is much prior art in this particular field, patented and not patented. The U.S. Patents Nos. listed below are a sample of the patented prior art:
______________________________________ 1,687,819 1,851,722 2,073,429 2,546,280 2,632,606 2,699,903 2,994,488 3,127,125 3,197,153 3,346,208 3,799,465 3,915,281 4,099,601 4,471,486 4,625,931 ______________________________________
The holders used in butcher paper, wrapping paper and drafting paper and cloth constitute significant prior art since they comprise apparatus for keeping non dispensed paper from unrolling and apparatus tending to prevent the roll of paper from unrolling more material when a portion of material is being separated from the roll. One such apparatus commonly used comprises a blade having its long axis parallel to the axis of the roll, supported on a radial arm at each end of the blade with the blade resting on the surface of the roll and held there by the force of gravity. The weight of the blade is such that material can be parted and removed by tearing it along the blade without lifting the blade significantly off the roll. A key factor is the tearing strength of the material relative to the weight of the blade. The weight of the blade also presses it against the roll, providing a friction force which tends to prevent the roll from unrolling inadvertently.
This kind of apparatus can only be used with the roll axis horizontal and this is too restrictive to sales in current markets. Also selling price has a major influence on commercial success of paper holders in wide use and the cost of the blade type apparatus has been found to be prohibitive.
A significant advantage of the blade type apparatus is that the tension force required to unroll the material remains essentially constant and independent of the change in outside diameter of the roll of material as it is used up. In holders in which the tendency to unroll is inhibited by essentially constant friction forces applied near the axis of the roll, the tension force increases significantly as roll diameter decreases. This poses a problem, particularly with paper perforated to separate into sheets when the tension force is applied near either edge of the paper rather than at the center. A crucial compromise is required related to the tensile strength of the paper at the perforations. Strength suitable for the tension force needed to unroll the paper when the roll diameter is large is not suitable when the roll diameter has decreased, and vide verse. The force required to separate a towel from the roll also varies in different brands of paper towel.
This problem was addressed by Ancona et al in U.S. Pat. No. 4,741,486. Their apparatus comprises a tension bar 136 (lines 58-68, column 6 and lines 1-8 column 7) which "prevents undesirable pulling of additional sheets from roll 14 and also prevents the next sheet that is to be pulled from dangling freely." No mention is made of having the force applied to the roll by the tension bar vary such that the force needed to unroll paper is essentially constant and independent of roll diameter and it is considered not obvious from this patent to design the spring which moves the tension bar so that the tension needed to unroll paper is essentially constant. Also, the apparatus of Acuna et al is deemed to be such that it could not be marketed at a competitive price.
U.S. pat. Nos. 3,197,153 and 4,625,931 show rolls of sheet or strip material wound onto cores with the rotation of the cores frictionally restricted and with the frictional adjustable. Elastomeric drum 14 of the apparatus of U.S. Pat. No. 3,197,153 provides both friction of the core 10 on the drum and friction between the drum and the supporting mechanism. The apparatuses of these patents are considered to be too complicated and expensive to be commercially successful in paper towel holders and the like.
In consideration of the factors discussed above, a prime objective of the subject invention is provision of a holder for paper towels in which the tension required to unroll the towels is adjustable to compensate for effects of the diameter of the roll and characteristics of the material of the roll. A second objective is that the apparatus be simple enough to enable marketing the invention at a competitive price. A third objective is that the apparatus be usable with the roll vertical, horizontal or at any other angle.